Methods, nodes and system for establishing independent network paths

ABSTRACT

A method in a source node establishing independent network paths including a first and second router nodes connected to the source node over a first and second mutually independent networks. The source node includes a first interface towards the first network, associated with a path identifier for a first network path; a second interface towards a second network associated with a path identifier for a second network path, and is configured to select which of the first and second router nodes should be used for sending data from the source node to the destination node via the first and second network paths, wherein the source node is configured to select different router nodes for the first and second network paths.

TECHNICAL FIELD

The technology disclosed herein relates generally to the field ofcommunication systems, and in particular to methods, nodes and systemfor establishing independent network paths in a communication system.

BACKGROUND

Real time automation systems are sensitive to loss of data. Data can belost in such systems for several reasons, for instance due to errors onlinks or network devices, external electrical disturbances, radiodisturbances or resource problems in network devices. Any such failurewithin a real-time control system supervising, for instance, anelectrical system, may lead to severe consequences.

In order to reduce the risk of communication losses redundancy may beadded. In a layer-2 Ethernet network with ring topology all devices areconnected by two ports to the Ethernet network. A media redundancyprotocol manages reconfiguration if a link is broken. A drawback withthis method is that reconfiguration after failure takes time and anylost data has to be retransmitted, which entails delay. Another problemis that a ring is logically a single Ethernet network with littleprotection against disturbances such as intermittent link errors orbroadcast storms.

Another Layer-2 method uses a parallel Ethernet structure as defined inthe International Electrotechnical Commission (IEC) 62439-3 (ParallelRedundancy Protocol, PRP). A PRP network implements redundancy functionsin the communicating end nodes, which are each attached to two differentand completely separated Ethernet networks; the two Ethernets have nodirect connection. As long as one of the Ethernet networks isoperational the frame sent from a source node reaches the destinationnode, which receives only the first message and discards the duplicatemessage. Hence, no data is lost even if one of the networks would failand the PRP is a good option for use within an Internet Protocol (IP)subnetwork such as Ethernet.

US2006/0256768 describes a routing method in a communication networkminimizing overlap between two paths in the network over which anoriginal packet and its duplicate are sent.

Although PRP provides high reliability, it is limited to work onlywithin the IP subnetwork. The mentioned real-time automation systems maycomprise applications which are highly sensitive to loss of data alsofrom devices of remote networks and even a shorter disturbance in theremaining functioning IP subnetwork may then have critical effects.

SUMMARY

The present invention addresses the above-mentioned problems byproviding methods and nodes ensuring redundancy by establishing parallelindependent network paths over layer 3 networks.

The objective is according to an aspect achieved by a source node forestablishing independent network paths in a communication systemcomprising at least a first router node and a second router node, eachconnected to the source node over a first network and a second network,wherein the first and the second networks are mutually independent. Thesource node comprises a first interface towards the first network,wherein the first network and the first interface are associated with apath identifier for a first network path, and a second interface towardsa second network, wherein the second network and the second interfaceare associated with a path identifier for a second network path. Thesource node is configured to select which of the first and second routernodes should be used for sending data from the source node to thedestination node via the first network path and which of the first andsecond router nodes should be used for sending data to the destinationnode via the second network path, wherein the source node is configuredto select different router nodes for the first and second network paths.

The method enables an application of the source node to send duplicatedata using different network paths to distant destination nodes. By thenetwork paths being independent, i.e. not having any network links incommon, there is no single point of failure and a high reliability ofdata being duly delivered is provided. The network paths are availablesimultaneously, which ensures availability even if one of the local areanetworks would fail and require reconfiguration. The method providesimproved network availability, which is highly important and required ine.g. large process automation plants.

The objective is according to an aspect achieved by a method in a sourcenode for establishing independent network paths in a communicationsystem, comprising at least a first router node and a second routernode, each connected to the source node over a first network and asecond network, wherein the first and the second networks are mutuallyindependent. The source node comprises a first interface towards thefirst network, wherein the first network and the first interface areassociated with a path identifier for a first network path, and a secondinterface towards a second network, wherein the second network and thesecond interface are associated with a path identifier for a secondnetwork path. The method comprises selecting which of the first andsecond router nodes should be used for sending data from the source tothe destination node via the first network path and which of the firstand second router nodes should be used for sending data to thedestination node via the second network path, wherein the source node isconfigured to select different router nodes for the first and secondnetwork paths.

The objective is according to an aspect achieved by a computer programfor a source node for establishing independent network paths in acommunication system. The computer program comprises computer programcode, which, when executed on at least one processor on the source nodecauses the source node to perform the method as above.

The objective is according to an aspect achieved by a computer programproduct comprising a computer program as above and a computer readablemeans on which the computer program is stored.

The objective is according to an aspect achieved by a router node forenabling independent network paths in a communication system. Thecommunication system comprises at least a first network, a secondnetwork, a third network and a fourth network, wherein the first,second, third and fourth networks are mutually independent. The routernode comprises: a first interface towards the first network, wherein thefirst network and the first interface are associated with a pathidentifier for a first network path; a second interface towards thesecond network, wherein the second network and the second interface areassociated with a path identifier for a second network path; a thirdinterface towards the third network, wherein the third network and thethird interface are associated with a path identifier for the firstnetwork path; a fourth interface towards the fourth network, wherein thefourth network and the fourth interface are associated with a pathidentifier for the second network path. The router node is configured totransmit, to all nodes within the communication system: a unique nodeidentifier assigned to the router node, and network information, thenetwork information comprising one or more of: information about one ormore of the networks, information about nodes within the communicationsystem, information on which networks and nodes within the communicationsystem that are reachable using the router node by using the first andsecond network paths, respectively.

The objective is according to an aspect achieved by a method performedin a router node for enabling independent network paths in acommunication system comprising at least a first network, a secondnetwork, a third network and a fourth network, wherein the first,second, third and fourth networks are mutually independent. The routernode comprises: a first interface towards the first network, wherein thefirst network and the first interface are associated with a pathidentifier for a first network path; a second interface towards thesecond network, wherein the second network and the second interface areassociated with a path identifier for a second network path; a thirdinterface towards the third network, wherein the third network and thethird interface are associated with a path identifier for the firstnetwork path; a fourth interface towards the fourth network, wherein thefourth network and the fourth interface are associated with a pathidentifier for the second network path. The method comprisestransmitting, to all nodes within the communication system: a uniquenode identifier assigned to the router node, and network information,the network information comprising one or more of: information about oneor more of the networks, information about nodes within thecommunication system, information on which networks and nodes within thecommunication system that are reachable using the router node by usingthe first and second network paths, respectively.

The objective is according to an aspect achieved by a computer programfor a router node for enabling independent network paths in acommunication system. The computer program comprises computer programcode, which, when executed on at least one processor on the source nodecauses the source node to perform the method as above.

The objective is according to an aspect achieved by a computer programproduct comprising a computer program as above and a computer readablemeans on which the computer program is stored.

The objective is according to an aspect achieved by a communicationsystem for establishing independent network paths. The communicationssystem comprises at least a first and a second router node and a sourcenode, according to the above. A method in a communication system is alsoprovided.

Further features and advantages of the embodiments of the presentinvention will become clear upon reading the following description andthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically an environment in which embodimentsaccording to the present invention may be implemented.

FIG. 2 illustrates part of a communication system in which embodimentsaccording to the present invention may be implemented.

FIG. 3 illustrates a flow chart over steps of a method in a source nodein accordance with the present invention.

FIG. 4 illustrates schematically a source node and means forimplementing embodiments of the present invention.

FIG. 5 illustrates a flow chart over steps of a method in a router nodein accordance with the present invention.

FIG. 6 illustrates schematically a router node and means forimplementing embodiments of the present invention.

FIG. 7 illustrates a flow chart over steps of a method in acommunication system in accordance with the present invention.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth such as particulararchitectures, interfaces, techniques, etc. in order to provide athorough understanding. In other instances, detailed descriptions ofwell-known devices, circuits, and methods are omitted so as not toobscure the description with unnecessary detail. Same reference numeralsrefer to same or similar elements throughout the description.

For sake of completeness and in order to provide thorough understandingof the present invention, a few aspects of communication networks areinitially briefly described.

The Internet protocol suite, also denoted Transmission ControlProtocol/Internet Protocol (TCP/IP) protocol stack, comprises a numberof layers. For the sake of clarity, it may be noted that the Internetprotocol suite does not correspond directly to the Open SystemsInterconnection (OSI) model, e.g. since TCP/IP may not use certain OSIlayers at all or may combine several OSI layers into a single layer. Inthe TCP/IP protocol stack hence:

Layer 1 is the physical network, e.g. Ethernet. Layer 1 specifies, forinstance, physical characteristics of the communication media, such ashardware standards.

Layer 2 is the data link layer, defining a local communication linkbetween two entities of the local network. The local network may e.g. bean Ethernet network, and an example of protocols used in the data linklayer is thus Ethernet-related Institute of Electrical and ElectronicsEngineers (IEEE) protocols. The two entities within the local networkcommunicate over e.g. Ethernet without any intervening routers.

Ethernet is used throughout this description as an example of Layer 1and layer 2 implementation, but it is noted that other local areanetworks and corresponding protocols could be used, e.g. wireless localarea networks such as e.g. Wi-Fi and that the invention is not limitedto Ethernet as the local area networks.

Layer 3 is the network layer, also known as the Internet layer usinge.g. Internet Protocol (IP). The Internet layer accepts and deliverspackets for the Ethernet network across different networks, i.e.establishes inter-networking. The Internet layer thus involves routers,and a first IP router of a first Ethernet may for instance route packetsto a second IP router of a second Ethernet on their way to their enddestination. It is noted that a layer 3 segment in an IP network issometimes also denoted a subnetwork. Such a subnetwork is formed by allnodes sharing the same network prefix as defined by its network mask.These nodes can then communicate directly on the layer 2 level (e.g.Ethernet).

Layer 4 is the transport layer, using e.g. TCP or User Datagram Protocol(UDP). The transport layer provides end-to-end communication and ensuresthat packets arrive in sequence by acknowledging packet reception andretransmitting lost packets.

The present invention is mostly concerned with and related to Layer 3,the Internet layer.

As indicated above, a router node is a device configured to forward datapackets between communication networks, and the router is henceconnected to two (or more) different networks. This is in contrast to aswitch node, which is configured to interconnect multiple networksegments at the data link layer. The router node reads addressinformation in an incoming data packet to determine its end destination.The router node directs the data packet to its next-hop node in the pathtowards the end destination node by using information in a routing tableor routing policy.

An end node, also denoted source node, as used herein denotes acommunication endpoint, i.e. a node initiating communication (datapackets) or being the end destination node (also denoted destinationnode herein) that receives the communication (data packets). The sourcenode may also be a destination node, and a router node may also be asource node or destination node.

FIG. 1 illustrates an environment in which embodiments of the presentinvention may be implemented. A communication system 1 is illustrated,in particular a data communications system. The communication system 1comprises at least two router nodes 2 a, 2 b (a first router node 2 aand a second router node 2 b) and two communicating end nodes 3 a, 3 b(a first end node 3 a and a second end node 3 b). The router nodes 2 a,2 b are Layer 3 router nodes, i.e. configured to convey data packetsbetween different communication networks.

According to an aspect of the invention, each router node 2 a, 2 b isconnected to at least four parallel local area networks A, B, C, D, e.g.Ethernet networks. Conversely, the four or more independent networks A,B, C, D are interconnected by at least two router nodes 2 a, 2 b. Thenetworks A, B, C, D are here denoted parallel and this should beunderstood as the networks A, B, C, D being completely separated, i.e.disjoint and operated in parallel. The end nodes 3 a, 3 b are dualattached nodes, i.e. each end node 3 a, 3 b is connected to two or morenetworks and may hence be seen as PRP-enabled nodes, which may send twocopies of a frame (data packet), over each respective network port (e.g.Ethernet ports in case of the network being an Ethernet network). It isnoted that each network A, B, C, D may comprise any number of connectednetwork nodes and devices (as illustrated in FIG. 2).

The first end node 3 a is in the following denoted source node 3 a andthe second end node 3 b is denoted destination node 3 b, although it isrealized that the communication may be in the reverse direction as well(from the second end node 3 b to the first end node 3 a). Each of thesource and destination nodes 3 a, 3 b is connected to the first andsecond router nodes 2 a, 2 b over at least at least two independentnetworks, e.g. Ethernets or other types of local area networks. In theexample illustrated in FIG. 1, the source node 3 a is connected to boththe first and the second router nodes 2 a, 2 b over both a first networkA and second network B. The source node 3 a may hence send data to thedestination node 3 b via the first router node 2 a over either the firstnetwork A or the second network B or via the second router node 2 b overeither the first network A or the second network B. Correspondingly, thedestination node 3 b is connected to both the first and the secondrouter nodes 2 a, 2 b over a third network C and a fourth network D. Thedestination node 3 b may hence receive data from the source node 3 a viathe first router node 2 a over either the third network C or the fourthnetwork D or via the second router node 2 b over either the thirdnetwork C or the fourth network D.

As a particular example, the source node 3 a may be a device in aprocess automation system, such as e.g. a power plant. The source node 3a may for instance be configured to send data such as process data,control data, process control data, etc. An application of the sourcenode 3 a may be configured for such sending of data. The data is oftentime critical and is sent to the destination node 3 b, which may, forinstance, be a device of a remotely located control and maintenancecenter or a server of an external packet data network.

FIG. 2 illustrates the source node 3 a being connected to the firstrouter node 2 a and the second router node 2 b over two networks: thefirst network A and the second network B. To this end, the source node 3a may comprise two network interfaces 6 a, 6 b (e.g. Ethernet interfacecomprising connectors, e.g. Ethernet ports) for the respective cabling,comprising e.g. Category 5 (Cat 5) cables, of the networks A, B. Thedestination node 3 b may correspondingly comprise two network interfaces(not illustrated).

It is realized that the communication system 1 may comprise numerousnetworks and network nodes besides the networks and nodes illustrated inFIG. 1. In FIG. 2 the first network A is illustrated as having connectedthereto the source node 3 a and the router node 2 a and also yet anadditional node 4 a. The second network B is illustrated as havingconnected thereto the source node 3 a and the router node 2 a and alsoanother additional node 4 b. These additional nodes 4 a and 4 b,respectively, may comprise any type of device, e.g. switches, hubs,actuators, sensors, any device of e.g. an automation system, etc. Eachsuch node may be connected to the first and the second router nodes 2 a,2 b, possibly via other nodes depending on the type of local areanetwork used. The first network A and the second network B are, asmentioned earlier, independent and any node of the first network Afailing does not affect the data delivery over the second network B. Ifusing different local area networks, e.g. a first local area networkcomprising Ethernet and a second local area network comprising Wi-Fi,these should also be independent (i.e. disjoint and operated inparallel).

In a corresponding manner as has been described for the source node 3 a,the destination node 3 b is also connected to the first and secondrouter nodes 2 a, 2 b over at least two local area networks, e.g.Ethernets: a third network C and a fourth network D.

It is noted that the network links between the nodes 2 a, 2 b, 3 a, 3 bmay be wired or wireless. It is also noted that FIG. 1 illustrates aminimum scenario in the sense that at least two communicating nodes areneeded, and at least two router nodes (layer 3 routers) for routing databetween the two communicating nodes 3 a, 3 b according to the invention.However, a larger number of nodes may be used, as described withreference to FIG. 2, and this is indeed the case in larger systems.

The communication system 1 may hence comprise still further router nodesinterconnecting different independent layer 2 networks. As a particularexample, the communication system 1 may comprise a fifth network and asixth network (not illustrated) comprising a third router node and afourth router node (not illustrated), each of the third and fourthrouter nodes, for instance, interconnecting the third network C and thefourth network D to a destination node over the fifth and sixth network.Such third and fourth router nodes would then provide the first andsecond router nodes 2 a, 2 b with further possibilities to reach desireddestination nodes.

According to aspects of the present invention, a method is provided forestablishing two parallel independent network paths through thecommunication system 1. With reference again to FIG. 1, a network pathfrom the source node 3 a to the destination node 3 b may pass throughthe first router node 2 a over either the first network A or over thesecond network B, and then over either the third network C or the fourthnetwork D. A network path from the source node 3 a to the destinationnode 3 b may also pass through the second router node 2 b over eitherthe first network A or over the second network B, and then over eitherthe third network C or the fourth network D.

In FIG. 1, a first network path P1 passes over the first network A tothe first router node 2 a and then over the third network C to thedestination node 3 b. A second network path P2 passes over the secondnetwork B to the second router node 2 b and then over the fourth networkD to the destination node 3 b. The first and second network paths P1, P2thus comprises (only) different network links and in particular alsopasses different router nodes 2 a, 2 b. By not following the samenetwork links and not passing the same router nodes 2 a, 2 b there areno single points of failure, i.e. no single node or link that could stopthe entire system from working. Thus, if for instance the third networkC encounters a failure there is still a functioning network path overthe fourth network D. As another example, if the first router node 2 afails, then there are still functioning network paths through the secondrouter node 2 b.

There are several possible paths between the source node 3 a and thedestination node 3 b. According to the present invention, it is ensuredthat different router nodes 2 a, 2 b are used, giving two independentnetwork paths over routed parallel networks simultaneously between thecommunicating source and destination nodes 3 a, 3 b. For instance, thefirst router node 2 a may provide a first network path P1 (source node 3a→network A→router node 2 a→network C→destination node 3 b) and thesecond router node 2 b may provide a second network path P2 (source node3 b→network B→router node 2 b→network D→destination node 3 b). The firstand second network paths P1, P2 are independent by using differentrouter nodes 2 a, 2 b and different, mutually independent networks A, B,C, D.

By using two layer 3 router nodes 2 a, 2 b as described a layer 3redundancy is provided. When the source node 3 a sets up a first andsecond independent network path P1, P2 through the communication system1 it is performed in such way that the first and second network pathsP1, P2 goes over different networks (e.g. Ethernets) as well as throughdifferent router nodes 2 a, 2 b.

The present invention thus ensures that the source node 3 a always usestwo independent network paths P1, P2 by selecting different router nodes2 a, 2 b for the network paths. To this end, the source node 3 acomprises a first interface towards the first network A. The firstnetwork A and a first interface to this first network A are associatedwith a path identifier for a first network path P1. The source node 3 aalso comprises a second interface towards a second network B. The secondnetwork B and the second interface to this second network B areassociated with a path identifier for a second network path P2. Thesource node 3 a may, at setting up of the layer 2 networks A, B (e.g.Ethernets), be provided with these first and second interfaces (e.g.Ethernet interfaces) towards the first and second networks A, B, andthis is typically then used onwards. From this it is realized that thefirst network A is always (if not reconfigured) used for the firstnetwork path P1 and that the second network B is always used for thesecond network path P2. However, it needs to be ensured that the networkpaths P1, P2 use different router nodes 2 a, 2 b.

The source node 3 a is therefore configured to select which of the firstand second router nodes 2 a, 2 b it should use for sending data to thedestination node 3 b via the first network path P1 and which of thefirst and second router nodes 2 a, 2 b it should use for sending data tothe destination node 3 b via the second network path P2. The selectionhas to be such that different router nodes 2 a, 2 b are selected for thefirst and second network paths P1, P2.

Each router node 2 a, 2 b sends “Network information” on all connectednetworks A, B, C, D to all neighbor nodes. In the communication system 1illustrated in FIG. 1, each router node 2 a, 2 b would send the “Networkinformation” to the source node 3 a and the destination node 3 b.

The “Network information” may comprise information about all networksand nodes reachable through this router node 2 a, 2 b on network paths,e.g. “P1” or “P2” path. Based on this, the source node 3 a may update arouting table and make the selection as required.

In particular, nodes 3 a, 3 b receiving the “Network information” mayupdate their local IP routing table and network status information forthe network paths, e.g. paths P1 and P2. For instance, the first routernode 2 a may be aware of a failure in the third network C, and “Networkinformation” may be sent informing about this, upon which the sourcenode 3 a and the destination node 3 b may need to update theirrespective IP routing table. Other examples of “Network information”comprise congestion information, link failures, node failures, distanceto nodes, central processing unit (CPU) load, network load etc.

An application of e.g. the source node 3 a may use the parallel networkpaths to send duplicate data to a remote receiving node, e.g.destination node 3 b. The application may obtain information about inwhich network (e.g. network D) the destination node 3 a resides. Theaddress of the destination node 3 b may, for instance, be knownbeforehand by the application or it may be acquired by the applicationfrom the source node 3 a (within which the application resides and isrun). The source node 3 a in turn may have received the destination node3 b address from the “Network information” information. It is noted thatthe application may acquire the destination node 3 b address in otherways as well. An application in the destination node 3 b may filter outthe data which is duplicate in any conventional manner.

According to embodiments of the present invention, all nodes 2 a, 2 b, 3a, 3 b are given unique node identities. The IP address of a node iscommonly used by routing protocols for identifying a node, but the nodeidentifier according to the present invention makes it possible toidentify a node in the network independently of its IP address. Theunique node identifier is used in order to avoid parallel network pathsto use the same router node. As mentioned earlier, by using differentrouter nodes for the different network paths, the network paths areensured to be independent. Each node 2 a, 2 b, 3 a, 3 b may also beconfigured with the conventional IP addresses for identification, e.g.one IP address for each network to which it is connected.

The end nodes of the communication system 1, e.g. the source node 3 a,comprises and maintains routing tables for selecting a particular routernode 2 a, 2 b for a particular network path P1, P2 in order to ensurethat the network paths are independent. The network path P1, P2 areindependent in the sense that they do not follow the same network linksand do not pass the same router nodes 2 a, 2 b. The independent pathsP1, P2 thereby have no single points of failure. Hence, there are nosingle points of failure that could prevent data communication betweenthe source node 3 a and the destination node 3 b. In contrast to priorart, the present invention provides a solution that is suitable forhighly time-critical applications. For instance, in a prior art solutionwherein redundancy is provided e.g. by a back-up node, are-configuration would be required for the replacement of the failednode with the back-up node. For highly time-critical applications thisis not a conceivable solution.

The end nodes 3 a, 3 b, may, for the purpose of the present invention,comprise a routing protocol configured to establish the at least twoindependent paths. Such routing protocol may select a path using an IProuting table as below:

Example on path selection using IP Routing table:

TABLE 1 Network IP Network mask Destination (netmask) Gateway (IProuter) 1^(st) path P1: Network C C netmask (e.g. Address of 1^(st)router 255.255.255.0) (e.g. 10.6.0.1) 2^(nd) path P2: Network D Dnetmask (e.g. Address of 2^(nd) router 255.255.255.0) (e.g. 10.6.59.1)

Network Destination may be the IP address of the packet's finaldestination (i.e. IP address of the destination node 3 b) or, asillustrated, a particular local area network of the destination node 3b.

IP Network mask (also denoted netmask) may be a subnet mask for aparticular IP address, used by the router node 2 a, 2 b to resolve whichpart of the IP address provides the network address (e.g. Network C) andwhich part of the address provides a node address (e.g. address of thedestination node 3 a). All nodes in e.g. the third network C have thesame network prefix, while the nodes have, according to the presentinvention, unique node identifiers.

From the routing table, information may be obtained on which gateway(which router node) the source node 3 a should use for the respectivenetwork paths P1, P2. The routing table indicates (in the column“Gateway”) that the first path P1 should use the first router node 2 aand that the second path P2 should use the second router node 2 b.

In order to ensure that the first path P1 and the second path P2 usedifferent router nodes 2 a, 2 b, the source node 3 a may select thefirst router node 3 a for the first path P1 (over the first network A)based on that the first router node 3 a has the lowest node identifier(e.g. lowest IP address, as exemplified in Table 1), while the secondrouter node 3 b is selected for the second path P2 (over the secondnetwork B) based on the second router node 3 b having the highest nodeidentifier (e.g. highest IP address). Various other ways of identifyingdifferent router nodes for the different paths P1, P2 to use differentrouter nodes are conceivable. For instance, the unique node identifiermay comprise a network unique name, a Globally unique identifier (GUID)or a Media Access Control (MAC) address. Although the IP addresses maybe used as router node identifiers, the use of e.g. GUID, MAC address ora network unique name is preferred over IP addresses since the lattermay be different depending on the network from which the router node isaccessed.

As mentioned earlier, the nodes receiving the “Network information” mayupdate their local IP routing table and network status information fornetwork paths, e.g. paths P1 and P2. Thereby the proper router node 2 a,2 b is always selected for a certain network path, and the desired atleast two independent network paths P1, P2 between the source node 3 aand the destination node 3 b are hence obtained.

It is noted that the routing table above is provided purely as anillustrative example, and that the routing table may comprise additionalor fewer parameters. For instance, the routing table may compriseinformation such as: Interface; which is the outgoing network interfacethat the end node 3 a should use when forwarding the packet to the nexthop or final destination; Next hop, which is the IP address of the nextnode on the path to the destination node 3 b and to which the packet isforwarded; Routes, which identifies directly-attached networks (A, B),and also identifies indirect networks (C, D) to which the end node 3 ais not directly connected, but can access through either of the first orsecond router nodes 2 a, 2 b; Metric, which may provide capacity,distance, transmission delay etc. for each available network path. Themetric may be helpful when the network paths are selected. The networkpaths for the same destination have equal capacity, distance andtransmission delay.

In various embodiments, all nodes 2 a, 2 b, 3 a, 3 b may send“Supervision information” on all connected networks to all neighbornodes. The “Supervision information” sent by a node may, for instance,comprise one or more of: its own node identity, its own IP address, anetwork Id “A” or “B” (or “C” or “D”). As has been noted earlier, thecommunication system 1 may comprise any number of nodes, and each suchnode may then send the “Supervision information” to their respectiveneighbor nodes.

An interface may also be provided, which may be implemented in one ormore nodes 2 a, 2 b, 3 a, 3 b or e.g. a workstation of the communicationsystem 1 in order to enable supervision of network paths to allreachable nodes. The “Supervision information” and “Network information”may be used as input and e.g. illustrative graphics may be provided bymeans of the interface, thereby enabling maintenance and/or supervisingpersonnel to easily see any problems (e.g. link failures) that mightarise.

The various features and embodiments that have been described may becombined in many different ways, examples of which are given in thefollowing with reference to FIG. 3.

FIG. 3 illustrates a flow chart over steps of a method in a networkdevice in accordance with the present invention.

A method 20 is provided for establishing independent network paths P1,P2 in a communications system 1. The communications system 1 comprisesat least a first router node 2 a and a second router node 2 b, eachconnected to the source node 3 a over a first network A and a secondnetwork B, wherein the first and the second networks A, B are mutuallyindependent. The method 20 may be performed in a sending end node 3 a(source node 3 a) for sending data to a receiving end node 3 b(destination node 3 b).

The source node 3 a comprises a first interface towards the firstnetwork A, wherein the first network A and the first interface areassociated with a path identifier for a first network path P1.

The source node 3 a comprises a second interface towards a secondnetwork B, wherein the second network B and the second interface areassociated with a path identifier for a second network path P2.

The method 20 comprises selecting 21 which of the first and secondrouter nodes 2 a, 2 b should be used for sending data from the sourcenode 3 a to the destination node 3 b via the first network path P1 andwhich of the first and second router nodes 2 a, 2 b) should be used forsending data to the destination node 3 b via the second network path P2,wherein the source node 3 a is configured to select different routernodes 2 a, 2 b for the first and second network paths P1, P2.

The method 20 ensures that all network links of the first network pathP1 differs from the network links of the second network path P2. Thenetwork paths P1, P2 are independent by using different network linksand different router nodes 2 a, 2 b (in particular layer-3 router nodes2 a, 2 b). The method 20 enables two paths that are activesimultaneously. The source node 3 a, 3 b may find at least two parallelpaths at the same time, which is highly valuable especially in largenetworks within which error sensitive and/or loss sensitive data issent. The network paths P1, P2 are independent in the sense that theyuse different network links and different router nodes 2 a, 2 b, whereinthe network paths P1, P2 have no network link or node in common.

In an embodiment, the selecting 21 comprises setting up a routing tablecomprising routing information for sending data to the destination node3 b reachable via the first and the second router nodes 2 a, 2 b,wherein the routing information specifies which of the first and secondrouter nodes 2 a, 2 b should be selected for sending data to thedestination node 3 b via the first network path P1 and which of thefirst and second router nodes 2 a, 2 b should be selected for sendingdata to the destination node 3 b via the second network path P2, whereinthe routing information defines different router nodes 2 a, 2 b for thefirst and second network paths P1, P2.

In some embodiments, the source node 3 a is assigned a unique nodeidentifier and the method 20 comprises exchanging supervisioninformation on the first and the second networks A, B respectively withall neighbor nodes 2 a, 2 b, which supervision information comprises oneor more of: the unique node identifier, information on addressesassociated with the first and second interfaces respectively, andinformation on network identities associated with the first and secondnetworks A, B. By exchanging supervision information between the nodes,supervision of the communication system is enabled. The supervisioninformation may, for instance, be used as input to graphicallyillustrating network paths and possible problems related thereto.

In various embodiments, the unique node identifier comprises one of: anetwork unique name, a Globally unique identifier (GUID) or a MediaAccess Control (MAC) address. The selected network paths P1, P2 to thedestination node 3 b may comprise establishing network paths P1, P2having equal capacity, equal distance and/or equal transmission delay.By establishing that the network paths have equal capacity and/or equaldistance and/or equal transmission delay, an error occurring on eithernetwork path will not affect the performance from the viewpoint of theapplication that is sending/receiving data.

In various embodiments, the first and second router nodes 2 a, 2 b areassociated with unique node identifiers respectively and the method 20comprises selecting the router node 2 a, 2 b having the lowest uniquenode identifier as the router node for sending data to the destinationnode 3 b via the first network path P1 and the router node 2 a, 2 bhaving the highest unique node identifier as the router node for sendingdata to the destination node 3 b via the second network path P2.

In various embodiments, the method 20 comprises receiving networkinformation from one or both of the first router node 2 a and the secondrouter node 2 b and/or a neighboring node 4 a and updating the routingtable with the network information.

In variations of the above embodiment, the network information comprisesone or more of: information about one or more of the networks A, B, C,D, information about nodes within the communications system 1,information on which networks A, B, C, D and/or nodes within thecommunications system 1 that are reachable using the first router node 2a and information on which networks A, B, C, D and/or nodes within thecommunications system 1 that are reachable using the second router node2 b.

In various embodiments, the method 20 comprises replicating data to besent to the destination node 3 b and sending the data in parallel overthe first network path P1 and the second network path P2 to thedestination node 3.

In various embodiments, the first router node 2 a and the second routernode 2 b comprise layer 3 routers.

FIG. 4 illustrates schematically a source node 3 a, 3 b and means forimplementing embodiments of the present invention.

The source node 3 a, 3 b comprises a processor 30 comprising anycombination of one or more of a central processing unit (CPU),multiprocessor, microcontroller, digital signal processor (DSP),application specific integrated circuit etc. capable of executingsoftware instructions stored in a memory 31 which can thus be a computerprogram product 31. The processor 30 can be configured to execute any ofthe various embodiments of the method for instance as described inrelation to FIG. 3.

The memory 31 can be any combination of read and write memory (RAM) andread only memory (ROM), Flash memory, magnetic tape, Compact Disc(CD)-ROM, digital versatile disc (DVD), Blu-ray disc etc. The memory 31may also comprise persistent storage, which, for example, can be anysingle one or combination of magnetic memory, optical memory, solidstate memory or even remotely mounted memory.

The source node 3 a, 3 b also comprises an interface 33 for instance aninput/output device for communicating with other network nodes. Suchinterface 33 may comprise a wireless communication interface and/or awired communication interface (e.g. Ethernet). The source node 3 a, 3 bcomprises in particular a first interface towards a first network A anda second network B, for instance Ethernet networks.

The source node 3 a, 3 b may thus also comprise one or more interfacesin the form of protocols e.g. IP protocols, Ethernet protocols etc.,schematically indicated at reference numeral 34. Further, the sourcenode 3 a, 3 b comprises a routing table 35, e.g. as described earlier.

The source node 3 a, 3 b may comprise an application 36 configured tosend data to a destination node. Examples of such applications comprisefor instance an IEC 61131 application communicating over the networkswith several Input/Output (I/O) devices connected to a subnetwork.

The present invention provides computer programs 32 for the source node3 a, 3 b. The computer program 32 comprises computer program code,which, when executed on at least one processor 30 of the source node 3a, 3 b causes the source node 3 a, 3 b to perform the method 20according to any of the described embodiments thereof.

The present invention also encompasses computer program products 31comprising a computer program 32 for implementing the embodiments of themethod as described, and a computer readable means on which the computerprogram 32 is stored. The computer program product 31 may, as mentionedearlier, be any combination of random access memory (RAM) or read onlymemory (ROM), Flash memory, magnetic tape, Compact Disc (CD)-ROM,digital versatile disc (DVD), Blu-ray disc etc.

The invention provides a source node 3 a for establishing independentnetwork paths P1, P2 in a communication system 1 comprising at least afirst router node 2 a and a second router node 2 b, each connected tothe source node 3 a over a first network A and a second network B,wherein the first and the second networks A, B are mutually independent.The source node 3 a comprises a first interface towards the firstnetwork A, wherein the first network A and the first interface areassociated with a path identifier for a first network path P1; and asecond interface towards a second network B, wherein the second networkB and the second interface are associated with a path identifier for asecond network path P2.

The source node 3 a is configured to select which of the first andsecond router nodes 2 a, 2 b should be used for sending data from thesource node 3 a to the destination node 3 b via the first network pathP1 and which of the first and second router nodes 2 a, 2 b should beused for sending data to the destination node 3 b via the second networkpath P2, wherein the source node 3 a is configured to select differentrouter nodes 2 a, 2 b for the first and second network paths P1, P2.

The source node 3 a may be configured to perform the above step e.g. bycomprising one or more processors 30 and memory 31 the memory 31containing instructions executable by the processor 30 whereby the endnode 3 a is operative to perform the step.

In different embodiments, the source node 3 a is configured to performthe method 20 according to any of the described embodiments.

In an embodiment, the source node 3 a is configured to select by beingconfigured to set up a routing table comprising routing information forsending data to the destination node 3 b reachable via the first and thesecond router nodes 2 a, 2 b. The routing information specifies which ofthe first and second router nodes 2 a, 2 b should be selected forsending data to the destination node 3 b via the first network path P1and which of the first and second router nodes 2 a, 2 b should beselected for sending data to the destination node 3 b via the secondnetwork path P2. Further, the routing information defines differentrouter nodes 2 a, 2 b for the first and second network paths P1, P2.

In an embodiment, the source node 3 a is assigned a unique nodeidentifier and configured to exchange supervision information over thefirst and the second networks A, B respectively with all neighbor nodes2 a, 2 b. The supervision information comprises one or more of: theunique node identifier, information on addresses associated with thefirst and second interfaces respectively, and information on networkidentities associated with the first and second networks A, B.

In an embodiment, the first and second router nodes 2 a, 2 b areassociated with unique node identifiers respectively and the source nodeis configured to select the router node 2 a, 2 b having the lowestunique node identifier as the router node for sending data to thedestination node 3 b via the first network path P1 and the router node 2a, 2 b having the highest unique node identifier as the router node forsending data to the destination node 3 b via the second network path P2.

In an embodiment, the source node 3 a is configured to receive networkinformation from one or both of the first router node 2 a and the secondrouter node 2 b and/or a neighboring node 4 a and updating the routingtable with the network information.

In various embodiments, the network information comprises one or moreof: information about one or more of the networks A, B, C, D,information about nodes within the communications system 1, informationon which networks A, B, C, D and/or nodes within the communicationssystem 1 that are reachable using the first router node 2 a andinformation on which networks A, B, C, D and/or nodes within thecommunications system 1 that are reachable using the second router node2 b.

In an embodiment, the source node 3 a is configured to replicate data tobe sent to the destination node 3 b and to send the data in parallelover the first network path P1 and the second network path P2 to thedestination node 3 b. The destination node 3 b, e.g. an applicationthereon, may be configured to receive a first received data packet anddiscard the duplicate one received later.

FIG. 5 illustrates a flow chart over steps of a method in a router nodein accordance with the present invention.

The method 40 may be performed in a router node 2 a, 2 b for enablingindependent network paths P1, P2 in a communication system 1 comprisingat least a first network A, a second network B, a third network C and afourth network D, wherein the first, second, third and fourth networksA, B, C, D are mutually independent. The router node 2 a, 2 b comprisesa first interface towards the first network A, wherein the first networkA and the first interface are associated with a path identifier for afirst network path P1.

The router node 2 a, 2 b comprises a second interface towards the secondnetwork B, wherein the second network B and the second interface areassociated with a path identifier for a second network path P2.

The router node 2 a, 2 b comprises a third interface towards the thirdnetwork C, wherein the third network C and the third interface areassociated with a path identifier for the first network path P1.

The router node 2 a, 2 b comprises a fourth interface towards the fourthnetwork D, wherein the fourth network D and the fourth interface areassociated with a path identifier for the second network path P2.

The first, second, third and fourth interfaces may comprise any type ofinterface, comprising hardware and/or software, and providing wired orwireless communication over the respective networks.

The method 40 comprises:

-   -   transmitting 41, to all nodes 3 a, 3 b, 4 a, 4 b within the        communication system 1:    -   a unique node identifier assigned to the router node 2 a, and    -   network information, the network information comprising one or        more of: information about one or more of the networks A, B, C,        D, information about nodes within the communication system 1,        information on which networks A, B, C, D and nodes within the        communication system 1 that are reachable using the router node        2 a, 2 b by using the first and second network paths P1, P2,        respectively. By transmitting, i.e. providing, its unique node        identifier and network information to e.g. the source node 2 a,        the source node is enabled to establish two independent network        paths P1, P2 to the destination node 3 b based thereon.

In an embodiment, the router node 2 a, 2 b is assigned a unique nodeidentifier and the method 40 comprises exchanging supervisioninformation on the first, second, third and fourth networks A, B, C, Drespectively with all neighbor nodes 2 a, 2 b, 3 a, 3 b, 4 a, 4 b) whichsupervision information comprises one or more of: the unique nodeidentifier, information on addresses associated with the first, second,third and/or fourth interfaces respectively, and information on networkidentities associated with the first, second, third and/or fourthnetworks A, B, C, D.

In an embodiment, the method 40 comprises updating a database withnetwork information and/or supervision information received from anynode 3 a, 3 b, 4 a, 4 b within the communication system 1.

FIG. 6 illustrates schematically a router node and means forimplementing embodiments of the present invention.

The router node 2 a, 2 b comprises a processor 50 comprising anycombination of one or more of a central processing unit (CPU),multiprocessor, microcontroller, digital signal processor (DSP),application specific integrated circuit etc. capable of executingsoftware instructions stored in a memory 31 which can thus be a computerprogram product 51. The processor 50 can be configured to execute any ofthe various embodiments of the method for instance as described inrelation to FIG. 5.

The memory 51 can be any combination of read and write memory (RAM) andread only memory (ROM), Flash memory, magnetic tape, Compact Disc(CD)-ROM, digital versatile disc (DVD), Blu-ray disc etc. The memory 51may also comprise persistent storage, which, for example, can be anysingle one or combination of magnetic memory, optical memory, solidstate memory or even remotely mounted memory.

The router node 2 a, 2 b also comprises a number of interfaces, at leastfour interfaces. In the figure a first interface 53, a second interface54, a third interface 55 and a fourth interface 56. The interfaces 53,54, 55, 56 may comprise any type of interface, any combination ofhardware and/or software adapted for communication with other networknodes. Such interfaces 53, 54, 55, 56 may comprise a wirelesscommunication interface and/or a wired communication interface (e.g.Ethernet). The router node 2 a, 2 b comprises in particular a firstinterface towards a first network A, a second network B, a third networkC and a fourth network D, for instance Ethernet networks. The routernode 2 a, 2 b may thus also four or more interfaces in the form ofprotocols e.g. IP protocols, Ethernet protocols etc.

The router node 2 a, 2 b further comprise or has access to a data baseor memory 57, for storing network information and/or supervisioninformation.

The present invention provides computer programs 52 for the router node2 a, 2 b. The computer program 52 comprises computer program code,which, when executed on at least one processor 50 of the router node 2a, 2 b causes the router node 2 a, 2 b to perform the method 40according to any of the described embodiments thereof.

The present invention also encompasses computer program products 51comprising a computer program 52 for implementing the embodiments of themethod as described e.g. in relation to FIG. 5, and a computer readablemeans on which the computer program 32 is stored. The computer programproduct 51 may, as mentioned earlier, be any combination of randomaccess memory (RAM) or read only memory (ROM), Flash memory, magnetictape, Compact Disc (CD)-ROM, digital versatile disc (DVD), Blu-ray discetc.

A router node 2 a, 2 b for enabling independent network paths P1, P2 ina communication system 1 is provided. The communication system 1comprises at least a first network A, a second network B, a thirdnetwork C and a fourth network D, wherein the first, second, third andfourth networks A, B, C, D are mutually independent. The router node 2a, 2 b comprises

-   -   a first interface towards the first network A, wherein the first        network A and the first interface are associated with a path        identifier for a first network path P1,    -   a second interface towards the second network B, wherein the        second network B and the second interface are associated with a        path identifier for a second network path P2,    -   a third interface towards the third network C, wherein the third        network C and the third interface are associated with a path        identifier for the first network path P1,    -   a fourth interface towards the fourth network D, wherein the        fourth network D and the fourth interface are associated with a        path identifier for the second network path P2.

The router node 2 a, 2 b is configured to transmit, to all nodes 3 a, 3b, 4 a, 4 b within the communication system 1:

-   -   a unique node identifier assigned to the router node 2 a, and    -   network information, the network information comprising one or        more of: information about one or more of the networks A, B, C,        D, information about nodes within the communication system 1,        information on which networks A, B, C, D and nodes within the        communication system 1 that are reachable using the router node        2 a, 2 b by using the first and second network paths P1, P2,        respectively.

In an embodiment, the router node 2 a, 2 b is assigned a unique nodeidentifier and configured to exchange supervision information on thefirst, second, third and fourth networks A, B, C, D respectively withall neighbor nodes 2 a, 2 b, 3 a, 3 b, 4 a, 4 b. The supervisioninformation comprises one or more of: the unique node identifier,information on addresses associated with the first, second, third and/orfourth interfaces respectively, and information on network identitiesassociated with the first, second, third and/or fourth networks A, B, C,D.

In an embodiment, the router node 2 a, 2 b is configured to update adatabase with network information and/or supervision informationreceived from any node 3 a, 3 b, 4 a, 4 b within the communicationsystem 1.

It is noted that the method 20 in the source node 3 a, described e.g.with reference to FIG. 3, and the method 40 in the router node 2 a, 2 b,described e.g. with reference to FIG. 5, may be performed in any of thenodes. That is, the router node may also act as source node as well asdestination node, and the source node of some data may be thedestination node for other data.

The present invention also comprises a communications system 1 as hasbeen described. In particular, a communication system 1 for establishingindependent network paths P1, P2 therein is provided. The communicationsystem 1 comprises at least a first router node 2 a and a second routernode 2 b, and at least a first network A, a second network B, a thirdnetwork C and a fourth network D, wherein the first, second, third andfourth networks A, B, C, D are mutually independent. Each router node 2a, 2 b comprises:

-   -   a first interface towards the first network A, wherein the first        network A and the first interface are associated with a path        identifier for a first network path P1,    -   a second interface towards a second network B, wherein the        second network B and the second interface are associated with a        path identifier for a second network path P2, and    -   a third interface towards the third network C, wherein the third        network C and the third interface are associated with a path        identifier for the first network path P1,    -   a fourth interface towards the fourth network D, wherein the        fourth network D and the fourth interface are associated with a        path identifier for the second network path P2, and    -   is configured to transmit, to all nodes 3 a, 3 b, 4 a, 4 b        within the communication system 1:    -   a unique node identifier assigned to the router node 2 a, and    -   network information, the network information comprising one or        more of: information about one or more of the networks A, B, C,        D, information about nodes within the communication system 1,        information on which networks A, B, C, D and nodes within the        communication system 1 that are reachable using the router node        2 a, 2 b by using the first and second network paths P1, P2,        respectively.

The description in relation to FIG. 6 on router nodes 2 a, 2 b isrelevant also here and may be referred to.

The communication system 1 further comprises a source node 3 acomprising:

-   -   a first interface towards the first network A, wherein the first        network A and the first interface are associated with a path        identifier for a first network path P1,    -   a second interface towards the second network B, wherein the        second network B and the second interface are associated with a        path identifier for a second network path P2, and    -   is configured to select which of the first and second router        nodes 2 a, 2 b should be used for sending data from the source        node 3 a to the destination node 3 b via the first network path        P1 and which of the first and second router nodes 2 a, 2 b        should be used for sending data to the destination node 3 b via        the second network path P2, wherein the source node 3 a is        configured to select different router nodes 2 a, 2 b for the        first and second network paths P1, P2.

The description in relation to FIG. 4 on source nodes 3 a, 3 b isrelevant also here and may be referred to. As mentioned earlier, thecommunication system 1 may comprise a larger number of independentnetworks, each comprising any number of nodes. For instance, thecommunication system 1 may comprise a fifth network, a sixth network, aseventh network and an eight network (not illustrated) interconnectedthrough various router nodes. The first and second router nodes 2 a, 2 bthen have further possibilities to reach a desired destination node.

FIG. 7 illustrates a flow chart over steps of a method in acommunication system 1 in accordance with the present invention.

A method 60 performed in a communication system 1 for establishingindependent network paths P1, P2 therein, the communication system 1comprising at least a first router node 2 a and a second router node 2b, and at least a first network A, a second network B, a third network Cand a fourth network D, wherein the first, second, third and fourthnetworks A, B, C, D are mutually independent. Each router node 2 a, 2 bcomprises:

-   -   a first interface towards the first network A, wherein the first        network A and the first interface are associated with a path        identifier for a first network path P1,    -   a second interface towards a second network B, wherein the        second network B and the second interface are associated with a        path identifier for a second network path P2, and    -   a third interface towards the third network C, wherein the third        network C and the third interface are associated with a path        identifier for the first network path P1,    -   a fourth interface towards the fourth network D, wherein the        fourth network D and the fourth interface are associated with a        path identifier for the second network path P2. The method 60        comprises transmitting (61), by each router node (2 a, 2 b) and        to all nodes 3 a, 3 b, 4 a, 4 b within the communication system        1:    -   a unique node identifier assigned to the router node 2 a, 2 b,        and    -   network information, the network information comprising one or        more of: information about one or more of the networks A, B, C,        D, information about nodes within the communication system 1,        information on which networks A, B, C, D and nodes within the        communication system 1 that are reachable using the router node        2 a, 2 b by using the first and second network paths P1, P2,        respectively,

The communication system 1 further comprises a source node 3 acomprising:

-   -   a first interface towards the first network A, wherein the first        network A and the first interface are associated with a path        identifier for a first network path P1,    -   a second interface towards the second network B, wherein the        second network B and the second interface are associated with a        path identifier for a second network path P2. The method 60        comprises    -   selecting 62, in the source node 3 a, which of the first and        second router nodes 2 a, 2 b should be used for sending data        from the source node 3 a to the destination node 3 b via the        first network path P1 and which of the first and second router        nodes 2 a, 2 b should be used for sending data to the        destination node 3 b via the second network path P2, wherein the        source node 3 a is configured to select different router nodes 2        a, 2 b for the first and second network paths P1, P2.

The description on method 20 in source node in relation to FIG. 3, andon method in router node 40 in relation to FIG. 5 are relevant also hereand may be referred to.

The invention has mainly been described herein with reference to a fewembodiments. However, as is appreciated by a person skilled in the art,other embodiments than the particular ones disclosed herein are equallypossible within the scope of the invention, as defined by the appendedpatent claims.

The invention claimed is:
 1. A source node configured to establishindependent network paths for a network layer, layer 3, through acommunication system, said communication system comprising at least afirst network and a second network being layer 3 networks, wherein thesource node: comprises a first interface connecting to a first routernode and to a second router node over the first network, wherein thefirst and second router nodes are layer 3 router nodes, and the firstnetwork and the first interface are associated with a path identifierfor a first network path, comprises a second interface connecting to thefirst router node and the second router node over the second network,wherein the second network and the second interface are associated witha path identifier for a second network path, and wherein the first andsecond networks are mutually independent layer 3 networks, beingdisjoint and operated in parallel, is configured to select which of thefirst and the second router nodes should be used for sending data to adestination node via the first network path and which of the first andsecond router nodes should be used for sending data to the destinationnode via the second network path, wherein the source node is configuredto select different router nodes for the first and second network paths.2. The source node as claimed in claim 1, configured to select which ofthe first and the second router nodes should be used for sending data tothe destination node via the first network path and which of the firstand second router nodes should be used for sending data to thedestination node via the second network path by using a routing tablecomprising routing information defining different router nodes for thefirst and second network paths.
 3. The source node as claimed in claim1, being assigned a unique node identifier and configured to exchangesupervision information over the first and the second networksrespectively with all neighbor nodes, which supervision informationcomprises one or more of: the unique node identifier, information onaddresses associated with the first and second interfaces respectively,and information on network identities associated with the first andsecond networks.
 4. The source node as claimed in claim 1, wherein thefirst and second router nodes are associated with unique nodeidentifiers respectively and the source node is configured to select therouter node having a lowest unique node identifier as the router nodefor sending data to the destination node via the first network path andto select the router node having a highest unique node identifier as therouter node for sending data to the destination node via the secondnetwork path.
 5. The source node as claimed in claim 1, configured toreceive network information from one or both of the first router nodeand the second router node and/or another neighbor node and to updatethe routing table with the network information.
 6. The source node asclaimed in claim 5, wherein the network information comprises one ormore of: information about one or more of the networks, informationabout nodes within the communications system, information on whichnetworks and/or nodes within the communications system that arereachable using the first router node and information on which networksand/or nodes within the communications system that are reachable usingthe second router node.
 7. The source node as claimed in claim 1,configured to replicate data to be sent in parallel over the firstnetwork path and the second network path to the destination node.
 8. Amethod performed in a source node for establishing independent networkpaths for a network layer, layer 3, through a communication system, saidcommunication system comprising at least a first network and a secondnetwork being layer 3 networks, the method comprising: selectingdifferent router nodes for a first and a second network paths byselecting which of a first router node and a second router node shouldbe used for sending data from the source node to a destination node viaa first network path, wherein the first network and a first interface ofthe source node are associated with a path identifier for the firstnetwork path, and which of the first and second router nodes should beused for sending data to the destination node via the second networkpath, wherein the second network and a second interface of the sourcenode are associated with a path identifier for the second network path,and wherein the first and second router nodes are layer 3 router nodesand the first and second networks are mutually independent layer 3networks, being disjoint and operated in parallel.
 9. The method asclaimed in claim 8, wherein the selecting comprises setting up a routingtable comprising routing information defining different router nodes forthe first and second network paths and selecting which of the first andsecond router nodes should be selected for sending data to thedestination node via the first network path and which of the first andsecond router nodes should be selected for sending data to thedestination node via the second network path using the routing table.10. The method as claimed in claim 8, wherein the source node isassigned a unique node identifier and the method comprises exchangingsupervision information on the first and the second networksrespectively with all neighbor nodes, which supervision informationcomprises one or more of: the unique node identifier, information onaddresses associated with the first and second interfaces respectively,and information on network identities associated with the first andsecond networks.
 11. The method as claimed in claim 8, wherein the firstand second router nodes are associated with unique node identifiersrespectively and wherein the method comprises selecting the router nodehaving the lowest unique node identifier as the router node for sendingdata to the destination node via the first network path and the routernode having the highest unique node identifier as the router node forsending data to the destination node via the second network path. 12.The method as claimed in claim 8, comprising receiving networkinformation from one or both of the first router node and the secondrouter node and/or another neighbor node and updating the routing tablewith the network information.
 13. The method as claimed in claim 12,wherein the network information comprises one or more of: informationabout one or more of the networks, information about nodes within thecommunications system, information on which networks and/or nodes withinthe communications system that are reachable using the first router nodeand information on which networks and/or nodes within the communicationssystem that are reachable using the second router node.
 14. The methodas claimed in claim 8, comprising replicating data to be sent inparallel over the first network path and the second network path to thedestination node.
 15. A non-transitory computer readable meanscomprising a computer program for a source node to establish independentnetwork paths for a network layer, layer 3, through a communicationsystem, said communication system comprising at least a first networkand a second network being layer 3 networks, the computer programcomprising computer program code, which, when executed on at least oneprocessor on the source node causes the source node to perform themethod according to claim
 8. 16. A router node enabling a source node toestablish independent network paths for a network layer, layer 3,through a communication system, said communication system comprising atleast a first network, a second network, a third network and a fourthnetwork being layer 3 networks, the router node being a layer 3 routernode and comprising: a first interface connecting to the first network,wherein the first network and the first interface are associated with apath identifier for a first network path, a second interface connectingto the second network, wherein the second network and the secondinterface are associated with a path identifier for a second networkpath, a third interface connecting to the third network, wherein thethird network and the third interface are associated with a pathidentifier for the first network path, a fourth interface connecting tothe fourth network, wherein the fourth network and the fourth interfaceare associated with a path identifier for the second network path,wherein the first, second, third and fourth networks are mutuallyindependent layer 3 networks, being disjoint and operated in parallel,and wherein the router node is configured to transmit, to all nodeswithin the communication system: a unique node identifier assigned tothe router node, and network information, the network informationcomprising one or more of: information about one or more of thenetworks, information about nodes within the communication system,information on which networks and nodes within the communication systemthat are reachable using the router node by using the first and secondnetwork paths, respectively.
 17. The router node as claimed in claim 16,being assigned a unique node identifier and configured to exchangesupervision information on the first, second, third and fourth networksrespectively with all neighbor nodes, which supervision informationcomprises one or more of: the unique node identifier, information onaddresses associated with the first, second, third and/or fourthinterfaces respectively, and information on network identitiesassociated with the first, second, third and/or fourth networks.
 18. Therouter node as claimed in claim 17, configured to update a database withnetwork information and/or supervision information received from anynode within the communication system.
 19. A method performed in a routernode for enabling a source node to establish independent network pathsfor a network layer, layer 3, through a communication system, saidcommunication system comprising at least a first network, a secondnetwork, a third network and a fourth network being layer 3 networks,the router node being a layer 3 router node, the method comprising:transmitting, to all nodes within the communication system: a uniquenode identifier assigned to the router node, and network information,the network information comprising one or more of: information about oneor more of the first, second, third and fourth networks that aremutually independent layer 3 networks, being disjoint and operated inparallel, wherein the first and third mutually independent networks anda first and a third interface of the router node are associated with apath identifier for a first network path and the second and fourthmutually independent networks and a second and a fourth interface of therouter node are associated with a path identifier for a second networkpath, information about nodes within the communication system,information on which networks, and nodes within the communication systemthat are reachable using the router node by using the first and secondnetwork paths, respectively.
 20. The method as claimed in claim 19,wherein the router node is assigned a unique node identifier and themethod comprises exchanging supervision information on the first,second, third and fourth networks respectively with all neighbor nodes,which supervision information comprises one or more of: the unique nodeidentifier, information on addresses associated with the first, second,third and/or fourth interfaces respectively, and information on networkidentities associated with the first, second, third and/or fourthnetworks.
 21. The method as claimed in claim 20, comprising updating adatabase with network information and/or supervision informationreceived from any node within the communication system.
 22. Anon-transitory computer readable means comprising a computer program fora router node for enabling a source node to establish independentnetwork paths for a network layer, layer 3, through a communicationsystem, said communication system comprising at least a first network, asecond network, a third network and a fourth network being layer 3networks, where the router node is a layer 3 router node, the computerprogram comprising computer program code, which, when executed on atleast one processor on the router node causes the router node to performthe method according to claim
 19. 23. A communication system forenabling a source node to establish independent network paths for anetwork layer, layer 3 through the communication system, saidcommunication system comprising at least a first router node and asecond router node, and at least a first network, a second network, athird network and a fourth network, wherein the first, second, third andfourth networks are mutually independent layer 3 networks, beingdisjoint and operated in parallel, wherein each router node is a layer 3router node and comprises: a first interface connecting to the firstnetwork, wherein the first network and the first interface areassociated with a path identifier for a first network path, a secondinterface connecting to the second network, wherein the second networkand the second interface are associated with a path identifier for asecond network path, and a third interface connecting to the thirdnetwork, wherein the third network and the third interface areassociated with a path identifier for the first network path, a fourthinterface connecting to the fourth network, wherein the fourth networkand the fourth interface are associated with a path identifier for thesecond network path, wherein each router node is configured to transmit,to all nodes within the communication system: a unique node identifierassigned to the router node, and network information, the networkinformation comprising one or more of: information about one or more ofthe networks, information about nodes within the communication system,information on which networks and nodes within the communication systemthat are reachable using the router node by using the first and secondnetwork paths, respectively, the communication system further comprisingthe source node comprising: a first interface connecting to a firstrouter node and to a second router node over the first network, whereinthe first network and the first interface are associated with a pathidentifier for the first network path and the first and second routernodes are layer 3 router nodes, a second interface connecting to thefirst router node and the second router node over the second network,wherein the second network and the second interface are associated witha path identifier for a second network path, and wherein the first andsecond networks are mutually independent layer 3 networks, is configuredto select which of the first and the second router nodes should be usedfor sending data to a destination node via the first network path andwhich of the first and second router nodes should be used for sendingdata to the destination node via the second network path, wherein thesource node is configured to select different router nodes for the firstand second network paths.
 24. A method performed in a communicationsystem for enabling a source node to establish independent network pathsfor a network layer, layer 3, through the communication system, saidcommunication system comprising at least a first router node and asecond router node, and at least a first network, a second network, athird network and a fourth network, wherein the first, second, third andfourth networks are, mutually independent layer 3 networks, beingdisjoint and operated in parallel, wherein each router node is a layer 3router node and comprises: a first interface towards the first network,wherein the first network and the first interface are associated with apath identifier for a first network path, a second interface towards thesecond network, wherein the second network and the second interface areassociated with a path identifier for a second network path, and a thirdinterface towards the third network, wherein the third network and thethird interface are associated with a path identifier for the firstnetwork path, a fourth interface towards the fourth network, wherein thefourth network and the fourth interface are associated with a pathidentifier for the second network path, and the method comprisestransmitting, by each router node and to all nodes within thecommunication system: a unique node identifier assigned to the routernode, and network information, the network information comprising one ormore of: information about one or more of the networks, informationabout nodes within the communication system, information on whichnetworks and nodes within the communication system that are reachableusing the router node by using the first and second network paths,respectively, the communication system further comprising the sourcenode comprising: a first interface towards the first network, whereinthe first network and the first interface are associated with a pathidentifier for a first network path, a second interface towards thesecond network, wherein the second network and the second interface areassociated with a path identifier for a second network path, and themethod comprises selecting, in the source node, which of the first andsecond router nodes should be used for sending data from the source nodeto the destination node via the first network path and which of thefirst and second router nodes should be used for sending data to thedestination node via the second network path, wherein the source node isconfigured to select different router nodes for the first and secondnetwork paths.